Dual free layer reader head with magnetic seed layer decoupled from shield

Abstract

The present disclosure generally relates to magnetic read heads comprising a dual free layer (DFL) structure. The magnetic read head comprises a first shield, a second shield, and a DFL structure disposed between the first and second shields. The DFL structure comprises a magnetic seed layer, a first free layer, and a second free layer. A non-magnetic spacer layer is disposed between and in contact with the first shield and the magnetic seed layer of the DFL structure at a media facing surface. A material and a thickness of the non-magnetic spacer layer is selected to control the coupling between the first shield and the magnetic seed layer of the DFL structure.

What is claimed is: 
     
       1. A magnetic read head assembly, comprising:
 a first shield; 
 a second shield disposed over the first shield; 
 a dual free layer (DFL) structure disposed between the first shield and the second shield at a media facing surface (MFS), the DFL structure comprising:
 a magnetic seed layer disposed over the first shield; 
 a first free layer disposed over the magnetic seed layer, the first free layer being disposed in contact with a non-magnetic seed layer; and 
 a second free layer disposed over the first free layer; and 
 
 a non-magnetic spacer layer disposed between the first shield and the magnetic seed layer of the DFL structure at the MFS. 
 
     
     
       2. The magnetic read head assembly of  claim 1 , wherein the non-magnetic spacer layer has a thickness greater than or equal to about 2 nm, wherein the first shield has a thickness between about 10 nm to about 2000 nm, and wherein the magnetic seed layer has a thickness between about 10 nm to about 60 nm. 
     
     
       3. The magnetic read head assembly of  claim 1 , wherein the non-magnetic spacer layer is configured to decouple the first shield from the magnetic seed layer, and wherein the non-magnetic spacer layer has a greater stripe height extending from the MFS into the magnetic read head assembly than the first and second free layers and a greater width in a cross-track direction at the MFS than the first and second free layers. 
     
     
       4. The magnetic read head assembly of  claim 1 , wherein the DFL structure further comprises:
 a barrier layer disposed between the first free layer and the second free layer; and 
 a cap layer disposed between the second free layer and the second shield, wherein the non-magnetic seed layer is disposed in contact with the magnetic seed layer, and wherein a material and a thickness of the non-magnetic spacer layer is selected to control a coupling strength between the first shield and the magnetic seed layer. 
 
     
     
       5. The magnetic read head assembly of  claim 1 , further comprising a rear hard bias (RHB) structure disposed adjacent to the DFL structure, the RHB structure being recessed from the MFS. 
     
     
       6. The magnetic read head assembly of  claim 1 , wherein the non-magnetic spacer layer is deposited as a part of the first shield. 
     
     
       7. A magnetic recording device, comprising:
 a magnetic read head assembly comprising:
 a first shield; 
 a second shield disposed over the first shield; 
 a dual free layer (DFL) structure disposed between the first shield and the second shield at a media facing surface (MFS), the DFL structure comprising:
 a magnetic seed layer disposed over the first shield; 
 a first free layer disposed over the magnetic seed layer, the first free layer being disposed in contact with a non-magnetic seed layer; and 
 a second free layer disposed over the first free layer; and 
 
 a non-magnetic spacer layer disposed between the first shield and the magnetic seed layer of the DFL structure at the MFS. 
 
 
     
     
       8. A magnetic read head assembly, comprising:
 a first shield; 
 a non-magnetic spacer layer disposed on and in contact with the first shield, the non-magnetic spacer layer being disposed at a media facing surface (MFS); 
 a tunnel magnetic resistive (TMR) sensor disposed on the non-magnetic spacer layer at the MFS, the TMR sensor comprising:
 a magnetic seed layer disposed on and in contact with the non-magnetic spacer layer; 
 a non-magnetic seed layer disposed on and in contact with the magnetic seed layer; 
 a first free layer disposed over the magnetic seed layer, the first free layer being disposed in contact with the non-magnetic seed layer; and 
 a second free layer disposed over the first free layer; and 
 
 a second shield disposed over the second free layer of the TMR sensor, 
 wherein the non-magnetic spacer layer is configured to control a coupling of the first shield and the magnetic seed layer. 
 
     
     
       9. The magnetic read head assembly of  claim 8 , wherein the first and second free layers have a first cross-track width at the MFS and a first stripe height extending from the MFS into the magnetic read head assembly, and wherein the non-magnetic spacer layer has a second cross-track width at the MFS greater than the first cross-track width and a second stripe height greater than the first stripe height. 
     
     
       10. The magnetic read head assembly of  claim 9 , wherein the non-magnetic spacer layer has a thickness greater than or equal to about 2 nm to decouple the first shield and the magnetic seed layer, and wherein the non-magnetic spacer layer comprises a material selected from the group consisting of Ru, Ta, CoHf, Cr, CoB, or a combination thereof. 
     
     
       11. The magnetic read head assembly of  claim 8 , wherein the TMR sensor further comprises:
 a barrier layer disposed between and in contact with the first free layer and the second free layer; and 
 a cap layer disposed between and in contact with the second free layer and the second shield, wherein the non-magnetic spacer layer is deposited as a part of the TMR sensor. 
 
     
     
       12. The magnetic read head assembly of  claim 8 , wherein the non-magnetic spacer layer extends adjacent to a rear hard bias (RHB) structure, the RHB structure being recessed from the MFS, wherein a shield-to-shield spacing of the first shield and the second shield is between about 14 nm to about 25 nm. 
     
     
       13. The magnetic read head assembly of  claim 8 , wherein a material and a thickness of the non-magnetic spacer layer is selected to control a coupling strength between the first shield and the magnetic seed layer. 
     
     
       14. A magnetic recording device, comprising:
 a magnetic read head assembly comprising:
 a first shield; 
 a non-magnetic spacer layer disposed on and in contact with the first shield, the non-magnetic spacer layer being disposed at a media facing surface (MFS); 
 a tunnel magnetic resistive (TMR) sensor disposed on the non-magnetic spacer layer at the MFS, the TMR sensor comprising:
 a magnetic seed layer disposed on and in contact with the non-magnetic spacer layer; 
 a non-magnetic seed layer disposed on and in contact with the magnetic seed layer; 
 a first free layer disposed over the magnetic seed layer, the first free layer being disposed in contact with the non-magnetic seed layer; and 
 a second free layer disposed over the first free layer; and 
 
 a second shield disposed over the second free layer of the TMR sensor, 
 wherein the non-magnetic spacer layer is configured to control a coupling of the first shield and the magnetic seed layer. 
 
 
     
     
       15. A magnetic read head assembly, comprising:
 a first shield; 
 a second shield disposed over the first shield; 
 a dual free layer (DFL) structure disposed between the first shield and the second shield at a media facing surface (MFS), the DFL structure comprising:
 a magnetic seed layer disposed over the first shield; 
 a non-magnetic seed layer disposed on and in contact with the magnetic seed layer; 
 a first free layer disposed on and in contact with the non-magnetic seed layer; 
 a barrier layer disposed on and in contact with the first free layer; 
 a second free layer disposed on and in contact with the barrier layer; and 
 a cap layer disposed on and in contact with the second free layer; and 
 
 a non-magnetic spacer layer disposed between and in contact with the first shield and the magnetic seed layer of the DFL structure at the MFS, the non-magnetic spacer layer having a thickness greater than or equal to about 2 nm. 
 
     
     
       16. The magnetic read head assembly of  claim 15 , wherein the non-magnetic spacer layer is deposited as a part of the DFL structure or as a part of the first shield. 
     
     
       17. The magnetic read head assembly of  claim 15 , wherein the first shield has a thickness between about 10 nm to about 2000 nm, and the magnetic seed layer has a thickness between about 10 nm to about 60 nm. 
     
     
       18. The magnetic read head assembly of  claim 15 , further comprising a rear hard bias (RHB) structure disposed adjacent to the DFL structure, the RHB structure being recessed from the MFS, wherein the first and second free layers have a first cross-track width at the MFS and a first stripe height extending from the MFS under the RHB structure, and wherein the non-magnetic spacer layer has a second cross-track width at the MFS greater than the first cross-track width and a second stripe height greater than the first stripe height. 
     
     
       19. The magnetic read head assembly of  claim 15 , wherein the non-magnetic spacer layer is configured to control a coupling of the first shield and the magnetic seed layer, and wherein the non-magnetic spacer layer comprises a material selected from the group consisting of Ru, Ta, CoHf, Cr, CoB, or a combination thereof. 
     
     
       20. A magnetic recording device, comprising:
 a magnetic read head assembly, comprising:
 a first shield; 
 a second shield disposed over the first shield; 
 a dual free layer (DFL) structure disposed between the first shield and the second shield at a media facing surface (MFS), the DFL structure comprising:
 a magnetic seed layer disposed over the first shield; 
 a non-magnetic seed layer disposed on and in contact with the magnetic seed layer; 
 a first free layer disposed on and in contact with the non-magnetic seed layer; 
 a barrier layer disposed on and in contact with the first free layer; 
 a second free layer disposed on and in contact with the barrier layer; and 
 a cap layer disposed on and in contact with the second free layer; and 
 
 a non-magnetic spacer layer disposed between and in contact with the first shield and the magnetic seed layer of the DFL structure at the MFS, the non-magnetic spacer layer having a thickness greater than or equal to about 2 nm.